Page:Outlines of Physical Chemistry - 1899.djvu/27

 THE GASEOUS STATE

��Now, the gas under investigation weighs g grams ; therefore, its density will be

o + 0-00129 * v A =^g+^o # p (1 + a t) 000129^ v

Several methods for the determination of g, p, v, and t have been proposed. Dumas, Gay-Lussac, and Hofmann have elaborated classical methods which are described in every text-book on physics. In chemical laboratories V. Meyer* s displacement method is pre- ferably followed.

In the figure (fig. 1) a repre- cubic centimetres capacity. The vertical tube, b, has an internal diameter of three to four milli- metres, and the lateral branch, c, is a capillary tube. The interior of this apparatus is dried by means of a current of hot air then introduced into the bath d ; and the pneumatic trough e is so adjusted that the opening of the capillary tube is under water.

The bath contains a liquid whose boiling point is at least fifty degrees higher than the boiling point of the substance FlG x

the vapour density of which is to

be determined. By means of a Bunsen burner, the flame of which can be easily regulated, the liquid in the bath is brought to boiling, so that the cylindrical bulb a is well enveloped in vapour. As the tube b is closed by a stopper, the air expelled by expansion escapes by the capillary tube and rises in bubbles through the water in the pneumatic

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